Please bear in mind that this question may be interpreted in more than one way, so there are several way that it may be answered correctly.
To me, Mayella Ewell's experiences with men of both the white and African-American races show very clearly that all men are equal, or are at least capable of being equal. Bob Ewell, Mayella's father, could have been a good man, just as Tom Robinson could have been a bad man. They both were given the choice of what kind of people they wanted to be, which is an undeniably important form of equality. Unfortunately, Bob Ewell chose to be an evil man. Tom Robinson, who certainly had the opportunity to be unkind, made the decision to be good, although he had no need to be.
Tom Robinson broke racial stereotypes by working for Mayella Ewell for free, which disproved the general belief held by much of Maycomb society that members of the black community were lazy and untrustworthy. The fact that he did not charge Mayella a fee for his labor also showed that he was not selfish or thoughtless. Tom Robinson embodied traits that are found in the best of people of any race.
Bob Ewell, despite being white, was dirty, mean, lazy, and ignorant. His actions encouraged his children to pattern their lives after his. Perhaps the worst of Bob Ewell's traits was his belief that he, in all of his filth (moral, hygienic, physical, etc.) had some innate right to destory another human being's life.
Tom Robinson and Bob Ewell could both have chosen to live the best life possible for themselves and their families, just as they could both have chosen to take advantage of those around them and refuse to treat anyone with respect. In this way, they were equals.